Are either sod and catalase or the polyamines involved in the paraquat resistance of Conyza canadensis ?

Abstract

Paraquat/atrazine coresistant (PqAR) and paraquat resistant (PqR) horseweed (Conyza canadensis /L./ Cronq.) plants showed ‐ in the first hour after 0.5 mM paraquat spraying ‐ a decreased catalase activity followed by a slight increase. However, the enzyme activity remained always below the initial value. Sensitive plants showed a significant increase of catalase activity in the first 4 hour after spraying. The transient character of paraquat inhibition, the recovery of photosyn‐thetic activity of the PqAR Conyza plants (characterized by variable fluorescence) after spraying remained unaffected by the Superoxide dismutase (SOD) inhibitor, diethyldithiocarbamate. This indicates that SOD is not involved in the resistance mechanism. Untreated resistant biotypes showed about 2.5 times higher total polyamine and putrescine level than the sensitive one. 100 μM of exogenously added putrescine was observed as having a protecting effect against paraquat in floated leaves of the sensitive biotype only. The resistant leaves were unaffected probably on account of their higher endogenous polyamine level. It is concluded that polyamines may play a role in the paraquat resistance of Conyza canadensis.     

Epibrassinolide ameliorates Cr (VI) stress via influencing the levels of indole-3-acetic acid, abscisic acid, polyamines and antioxidant system of radish seedlings

The present investigation determined the effects of epibrassinolide (EBL) on the levels of indole-3-acetic acid (IAA), abscisic acid (ABA), and polyamine (PA) and antioxidant potential of 7-d old Raphanus sativus L. cv. ‘Pusa chetki’ seedlings grown under Cr (VI) metal stress. Reduced titers of free (0.767 μg g⁻¹ FW) and bound (0.545 μg g⁻¹ FW) IAA in Cr (VI) stressed seedlings were observed over untreated control. Supplementations of EBL to Cr (VI) stressed seedlings were able to enhance both free (2.14-5.68 μg g⁻¹ FW) and bound IAA (2.45-7.78 μg g⁻¹ FW) concentrations in comparison to Cr (VI) metal treatment alone. Significant rise in free (13.49 μg g⁻¹ FW) and bound (12.17 μg g⁻¹ FW) ABA contents were noticed for Cr (VI) stressed seedlings when compared to untreated control. No significant increase in ABA contents were recorded for Cr (VI) stressed seedlings upon supplementation with EBL over Cr (VI) treatment alone. A significant increase in Put (18.40 μg g⁻¹ FW) and Cad (9.08 μg g⁻¹ FW) contents were found for 10⁻⁹ M EBL plus Cr (VI) metal treatments when compared to Cr (VI) treatment alone. Spermidine (Spd) contents were found to decline significantly for EBL treatment alone or when supplemented with Cr (VI) treatments over untreated controls and Cr (VI) treatment alone. Antioxidant levels were found to enhance, with glutathione (57.98 mg g⁻¹ FW), proline (4.97 mg g⁻¹ FW), glycinebetaine (39.01 μmol mL⁻¹), ascorbic acid (3.17 mg g⁻¹ FW) and phytochelatins (65.69 μmol g⁻¹ FW) contents noted for EBL supplemented to Cr (VI) metal solution over Cr (VI) treatment alone. Reduced activities of guaiacol peroxidase (0.391 U mg⁻¹ protein) and catalase (0.221 U mg⁻¹ protein) and enhanced activities of glutathione reductase (7.14 U mg⁻¹ protein), superoxide dismutase (15.20 U mg⁻¹ protein) and ascorbate peroxidase (4.31 U mg⁻¹ protein) were observed in seedlings treated with EBL plus Cr (VI) over Cr metal treatment alone. Reduced MDA (2.55 μmol g⁻¹ FW) and H₂O₂ (33.24 μmol g⁻¹ FW) contents were recorded for 10⁻⁹ M EBL supplemented to Cr (VI) stress over Cr (VI) treatment alone. Enhancement in free radical scavenging potential as indicated by higher values of 1,1-diphenylpicrylhydrazyl, deoxyribose and reducing power activity assays, and increased levels of phenols and soluble sugars also showed significant influence of EBL in alleviating Cr (VI) stress in radish seedlings.     

铅胁迫下黄瓜幼苗内源多胺变化动态的初步研究

以黄瓜幼苗为材料,采用高效液相色谱法测定黄瓜幼苗叶和茎中内源多胺的含量,研究了铅胁迫下黄瓜幼苗生长及内源多胺的变化。结果表明:铅质量浓度为100mg·L-1时促进黄瓜幼苗的生长,铅质量浓度高于100mg·L-1时,黄瓜幼苗茎高和根长逐渐下降;铅胁迫下黄瓜幼苗地上部的腐胺含量明显高于对照值,且随着铅质量浓度增加和处理时间的延长呈下降趋势。黄瓜幼苗叶片精胺和亚精胺在处理第5d时高于对照值,茎中精胺和亚精胺含量在处理第7d高于对照值,而其它时间内的都低于对照值,而且其含量均随铅质量浓度的增加而呈下降趋势;过氧化物酶活性变化与内源多胺含量(腐胺、精胺和亚精胺之和)的变化相似,表明铅胁迫能改变黄瓜幼苗内源多胺的含量和调节过氧化物酶活性,从而影响着黄瓜植株的生长。     

2011年春季东海赤潮演替过程中海水中的游离态多胺

利用高效液相色谱法测定了2011年东海赤潮演替过程中海水中的主要的游离态多胺腐胺、亚精胺和精胺的浓度.调查海区腐胺、亚精胺和精胺的浓度范围分别为0~48nmol/L,3~11nmol/L和2~17nmol/L,其中腐胺的平均浓度最高,亚精胺次之,精胺的浓度最低.从平面分布看,在4月份以中肋骨条藻为主的硅藻赤潮爆发期,和5月份以东海原甲藻为主的甲藻赤潮爆发期,赤潮爆发的区域多胺浓度相对较高;各个断面的多胺浓度随着赤潮爆发的过程发生变化,并且与DOC、POC、DON以及C/N等呈较明显的相关性.